F
Factor of Subdivision: Value used in the calculation of the permissible floodable length of a compartment with respect to the damage stability of a ship. The value is determined by a formula, which depends on the length of the ship and is measured by a criterion of service numeral. (A numeral based on the relation between the volume of space allotted to passengers and machinery and the total volume).
Fair: Term applied to the readjustment of ships plating that has become slightly buckled in a collision.
Fairlead: Fitting allowing ropes and mooring lines to go in the required direction unobstructed. Usually fitted in a gunwhale or ships rail at the foc’s’le or stern to facilitate a smooth entry of the mooring lines.
Falls: Rope and blocks attached to the davits for raising and lowering lifeboats.
Fashion Plate: Side plate at the end of the superstructure deck, generally with a curved end.
Fathom: Measurement of the depth of water and equal to 6 feet.
Feathering: 1) Positioning of the blades of a Controllable Pitch Propeller such that no thrust is generated, exactly the same as an aircraft propeller. 2) The release of small quantities of steam by a boiler safety valve as it approaches lift pressure.
Feed Tank: Storage tank for boiler feed water, usually a double bottom tank.
Feeder Ship: A smaller vessel that transfers cargoes from deep sea ports to smaller inland ports.
Fender: A resilient device, usually movable, interposed between a ships hull and the harbour walls or other vessels to minimize impact and prevent direct contact so reducing the risk of damage.
FEU: Forty Foot Equivalent Unit. Measurement of container capacity of container ships. Equal to two TEU’s, Twenty Foot Equivalent Units.
Fiddley: Generally regarded as the space inside the funnel where all the uptakes come together.
Fillet: Rounded corner cut in plate or machined in a casting or as originally cast to alleviate stress concentrations found at a sharp corner.
Fineness: The ratio of the area of a waterplane to the area of the circumscribing rectangle. It varies from about 0.7 for a fine form vessel like a yacht to about 0.9 for a full form vessel such as a tanker.
Flagstaff: A flagpole at the stern of a ship, which should be used to carry the ensign of the country of registration. For UK registered vessels that would be a Red Ensign for Merchant Navy, White Ensign for the Royal Navy and a Blue Ensign for RFA or a Merchant Navy Vessel with a Captain who is a member of the Royal Navy Reserves. Also known as Recd White and Blue Dusters.
Flanking Rudders: Additional rudders fitted in front of the propellers.
Flap Rudder: A rudder with a separate tail flap that moves in an angle greater than the main rudder. This gives much increased lift and can generate thrust at 90 deg to the vessel.
Flare: Outward curvature of the side plating at the forward end above the waterline.
Flat: Minor internal, usually lower, deck. Usually without sheer or camber hence its title.
Flat Margin: A double bottom construction where the tank top extends horizontally to the ships side.
Flat of Keel: Width of the horizontal portion of the bottom shell, measured transversely. Also called the Flat of Bottom.
Flat Plate Keel: Middle or center line strake of plating in the bottom shell. It is increased in thickness for strength and as a corrosion allowance.
Flettner Rudder: Specially designed flap rudder using two narrow flaps at the trailing edge, one above the other.
Floating Dry Dock: An often misinterpreted definition. The dock is basically a large “U” shaped tank open at both ends. The tank is sunk by filling it with water. The vessel sails in, the tank is pumped out and it rises, picking up the ship in the process until it is completely out of the water carrying the ship.
Floor Ceiling: Wood covering placed over the tank tops for protection.
Floor Plan: Horizontal section showing the ship divided at the waterline or a deck line.
Floors: Vertical (yes vertical!) plating mounted in the double bottom tanks. They can be watertight, creating tanks. The floor structure is continuous from the centre girder to the side shell and supports the inner bottom shell. The arrangement of flooring will be determined by the framing system adopted, which could be either transverse or longitudinal.
Fluke: The palm of the anchor, i.e. the broad flat portion that penetrates the seabed and holds the anchor. It is worth noting that the ship is not held by the anchor but by the cable lying on the seabed. The anchor simply holds the end of the cable for accurate positioning.
Flume: A stabilization system using an athwartships tunnel connecting two wing tanks, the combination containing a set amount of water. The water travels along the tunnel as the vessel heels thus causing a dampening affect on the motion.
Flush Deck: An upper deck extending along a ships length without side to side structures.
Flying Bridge: An open control position located above the enclosed wheelhouse.
Fore Peak: A watertight compartment between the watertight collision bulkhead and the stem frame. Usually a ballast tank.
Foc’s’le: or forecastle or focsle etc. A raised deck at the bow below which the crew were traditionally housed.
Fork Beam: A half beam used to support a deck where an opening such as a hatch occurs.
Forward Perpendicular: A vertical line drawn through the point at which the stem frame cuts the Summer Loadline.
Forward Shoulder: The part of the hull where the bow area meets the parallel midships area.
Frame: Transverse structural member acting as a stiffener to the internal hull plating. Can also be longitudinal and can also be referred to as the ribs of the hull.
Free Surface Effect: An effect that can reduce stability, which occurs when a tank is not fully filled and is said to be slack. Free surface effect is not dependant on the depth of liquid and the degree of instability is the same whether the tank is nearly full or nearly empty. This effect is reduced by the inclusion of internal open bulkheads, which allow the passage of the liquid, but reduces its movement.
Freeboard: The vertical distance from the summer Load waterline to the top of the freeboard deck plating, measured amidships. The freeboard bears a direct relationship on the vessels seaworthiness in as such as the greater the freeboard the more stable the vessel will be in the event of damage or ingress of water.
Freeboard Deck: Uppermost complete deck exposed to the elements with a system of watertight enclosures to ensure the watertight integrity is maintained.
Freeing Port: Opening in the Bulwark to allow the fast removal of water accumulated on deck.
Freeing Scuttle: Flap fitted to some freeing ports to allow water to drain out but not enter.
Funnel: Structure containing all the exhaust uptakes, taking them to a height where the exhaust can clear the ship.
Funnel Guy: Stays or braces supporting the funnel, usually attached to a circumferential ring around the funnel. More necessary on riveted funnel structures.
